zoomable android textview

目标=把helloworld的文字变成可以缩放的。

测试=需要能实体手机，虚拟机似乎不能进行触摸缩放测试。

版本=android 2.3.3，target=android-10

参考了网上例子。

关键点

=============main.xml

<TextView android:id="@+id/text"

android:layout_width="fill_parent"

android:layout_height="fill_parent"

android:text="@string/hello" />

=============A1Activity.java

public void onCreate中，加入：

TextView textView = (TextView) findViewById(R.id.text);

textView.setOnTouchListener(this);

加入public boolean onTouch和相关变量

public boolean onTouch中，最后return true;是关键。

关键文件代码

=============main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical" >

    <TextView android:id="@+id/text"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        android:text="@string/hello" />

</LinearLayout>

=============A1Activity.java

package com.ex.a1205;

import android.app.Activity;
import android.os.Bundle;
import android.util.FloatMath;
import android.util.Log;
import android.util.TypedValue;
import android.view.MotionEvent;
import android.view.View;
import android.view.View.OnTouchListener;
import android.widget.TextView;

public class A1Activity extends Activity implements OnTouchListener {
  private static final String TAG = "textZoom";
  // We can be in one of these 2 states
  static final int NONE = 0;
  static final int ZOOM = 1;
  int mode = NONE;

  static final int MIN_FONT_SIZE = 20;
  static final int MAX_FONT_SIZE = 150;

  float oldDist = 1f;

  @Override
  public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);
    TextView textView = (TextView) findViewById(R.id.text);
    textView.setOnTouchListener(this);
  }

  public boolean onTouch(View v, MotionEvent event) {
    TextView textView = (TextView) findViewById(R.id.text);
    switch (event.getAction() & MotionEvent.ACTION_MASK) {
    case MotionEvent.ACTION_POINTER_DOWN:
      oldDist = spacing(event);
      Log.d(TAG, "oldDist=" + oldDist);
      if (oldDist > 10f) {
        mode = ZOOM;
      }
      break;
    case MotionEvent.ACTION_POINTER_UP:
      mode = NONE;
      break;
    case MotionEvent.ACTION_MOVE:
      if (mode == ZOOM) {
        float newDist = spacing(event);
        if (newDist > 10f) {
          float scale = newDist / oldDist;

          if (scale > 1) {
            scale = 1.1f;
          } else if (scale < 1) {
            scale = 0.95f;
          }

          float currentSize = textView.getTextSize() * scale;
          if ((currentSize < MAX_FONT_SIZE && currentSize > MIN_FONT_SIZE)
              || (currentSize >= MAX_FONT_SIZE && scale < 1)
              || (currentSize <= MIN_FONT_SIZE && scale > 1)) {
            textView.setTextSize(TypedValue.COMPLEX_UNIT_PX, currentSize);
          }
        }
      }
      break;
    }
    return true;
  }

  /** Determine the space between the first two fingers */
  private float spacing(MotionEvent event) {
    float x = event.getX(0) - event.getX(1);
    float y = event.getY(0) - event.getY(1);
    return FloatMath.sqrt(x * x + y * y);
  }

}

执行结果

zoomable android textview

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